PROJECT SUMMARY Illness uncertainty refers to thoughts and perceptions about illness-related events that are unpredictable, ambiguous, and/or complex in nature. Higher levels of illness uncertainty consistently and robustly predict increased psychological distress in both parents and children (e.g., posttraumatic stress symptoms, anxiety, and depression). Therefore, strategies to decrease uncertainty are central to optimizing the adjustment of children with cancer and their parents. A recent pilot study conducted by our team evaluated acceptability and feasibility of the Parental Uncertainty Management Intervention (PUMI), a clinic-based interdisciplinary intervention for parents of children newly diagnosed with cancer. The goal of the PUMI is to help parents manage uncertainty in order to promote both parent adjustment and, subsequently, child adjustment in the context of a child's new cancer diagnosis. Parents in the PUMI group demonstrated significant improvements in maternal distress and child behavior problems compared to the treatment as usual group at 1- and 3-months post-treatment follow-ups. The proposed multisite trial will test the PUMI's efficacy and durability with regard to improving parent and child adjustment shortly following a child's cancer diagnosis. Parents of children between two and 18 years of age will be randomly assigned at baseline to either the PUMI or the Education/Support Only (ESO; attention control) condition. Both conditions consist of six-sessions that will be delivered jointly by a nurse and psychologist. The PUMI teaches parents to identify triggers that lead to uncertainty, utilize strategies to prevent those triggers, as well as manage uncertainty that is unavoidable. In addition, parents will have access to an on-line portal designed to increase knowledge and decrease perceived ambiguities about the child's illness and treatments. Parents in the ESO will also complete six in-clinic sessions with a nurse and psychologist. These sessions will provide education about pediatric cancer and social support. [Parents in both groups will complete measures of psychological distress, illness uncertainty, posttraumatic stress, problem- solving, and parent-reported child emotional and behavioral functioning at five time points: baseline, 1-week post-intervention, as well as 3-, 6-, and 12-months post-treatment. The primary aims for the proposed study are to compare the PUMI to the ESO group on parent and child psychological distress 1-week post- intervention. The secondary aims are to compare the durability of the PUMI to the ESO group on parent and child overall distress and posttraumatic stress symptoms. Potential mediators of the treatment effects, including levels of uncertainty and portal use, will also be examined.] This study will provide an empirically- supported intervention that will significantly mitigate the adverse impact pediatric cancer has on child and parent adjustment and, ultimately, advance the practice of comprehensive cancer care.